Processing of semi-conductor wafers into finished electronic components typically requires many processing steps where the wafers must be handled and processed. The wafers are very valuable, and are extremely delicate and easily damaged by physical and electrical shocks. In addition, successful processing requires the utmost in cleanliness, free of particulates and other contaminants. As a result, specialized containers or carriers have been developed for use during processing, handling and transport of wafers. These containers protect the wafers from physical and electrical hazards, and are sealable to protect the wafers from contaminants. An important characteristic of these containers is that they must be cleanable between uses to ensure that cleanliness is maintained as much as possible. Accordingly, ease of assembly and disassembly of the carrier is a desirable feature.
Various configurations of door enclosures and latching mechanisms for sealable wafer carriers are known in the art. Latching mechanisms known in the art often use rotatable cam members. These cam members have typically been formed of planar plastic plates with elongate recesses defining cam surfaces. In early designs, these cam surfaces only provided motion of the cam follower in one direction, typically a single back and forth radial direction that translated to an extension and retraction of the latching portions. Later, a latch motion in the axial direction of the cam member was introduced in order to provide a means of securing the wafer carrier door more tightly for sealing reasons. These axial translation means typically added a substantial number of component parts to the latch assembly. Such additional component parts increase manufacturing costs, increase the complexity of the latching mechanism, increase the difficulty in assembly and disassembly, and increase the number of rubbing and scraping surfaces which generate more particulates.
A rotatable cam actuated latching mechanism having an improved cam follower allowing the needed axial movement of a latching arm in addition to simple radial movement was disclosed in U.S. Pat. No. 5,957,292 incorporated fully herein by reference. That invention allowed for a secure door latching mechanism having fewer component parts and with less rubbing and scraping contact, in part due to an s-shaped cam follower that engaged and captured the cam member. The s-shaped cam follower, however, still required cam surfaces defined by an elongated slot in the cam. Such a slotted structure is more difficult to produce than a solid member. In addition, more manipulative steps are required to assemble the cam follower with the cam member.
Further improvement to the simplicity and ease of assembly for a door latching mechanism is needed and requires that a cam follower engage and capture the edge of a rotary cam member in some fashion.